I am thinking more of calling the other guy, have them kill it briefly and
see if the interference goes away. Then work out some solutions.
-----Original Message-----
From: Adam Moffett
Sent: Thursday, April 25, 2019 11:21 AM
To: [email protected]
Subject: Re: [AFMUG] Ducting mitigation
It is licensed, yes. If I knew where the signal came from, could I
figure out the angle of incidence?
It seems like the warm air layer is above you so it has to be coming
from above. Maybe we just put a climber on the tower in the AM and have
him tilt down 0.5 degree at a time until it goes away. There's a null
right above the main lobe, so I feel like if we tilt down slowly we can
put the signal in that null.
This is the map they're looking at by the way: http://aprs.mennolink.org/
-Adam
On 4/25/2019 12:48 PM, [email protected] wrote:
Downtilt will help assuming it is coming in at a particular sky angle, but
you may lose coverage by doing it. Be interesting if you could actually
find the source of the interference. 2.5 is licensed right?
If you could get a real accurate bearing on the interference you ought to
be able to look up who is on that line.
-----Original Message----- From: Adam Moffett
Sent: Thursday, April 25, 2019 10:40 AM
To: [email protected]
Subject: Re: [AFMUG] Ducting mitigation
Hmm....couldn't say. In the example they showed me it was clearly
coming from the west, but I don't know if it's the same every time.
Does the fact that it affects more than one tower at the same time tell
us anything? I couldn't get more separation than a separate tower.
Is down tilt likely to help at all or is that just chasing our tail?
On 4/25/2019 12:22 PM, [email protected] wrote:
Spatial diversity would work if the interference is always coming at the
exact same angle.
Is the interference always coming from one direction?
-----Original Message----- From: Adam Moffett
Sent: Thursday, April 25, 2019 10:01 AM
To: AnimalFarm Microwave Users Group
Subject: [AFMUG] Ducting mitigation
I'm trying to help some associates in the Southeast who seem to have an
issue with ducting.
They have a number of 2.5ghz Telrad base stations. During the mornings
in the springtime they'll get an interfering signal on multiple base
stations at the same time. The strength of this signal is pretty
ridiculous whatever it is. Last spring they struggled to explain where
this was coming from, and initially were exploring things like return
loss on cables or self interference. They found an online map of
tropospheric ducting conditions and apparently they find that whenever
the issue pops up they can pull up this ducting map and see a big red
blob on top of their locations. This spring they're getting about the
same experience. The fact that it happens like clockwork every morning
and that it can be reliably predicted by this online tropospheric
ducting map has them pretty convinced.
The question is what can they do about it?
My first thought was increase down tilt until the sector can't see over
the horizon. They could try spatial diversity, but I don't know how far
apart the antennas would have to be to make a difference. Any thoughts
on that? Any thoughts on other solutions? The problem will go away in
mid may (until next year), so whatever they try has to be done in the
next couple of weeks.
-Adam
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